1. Technical Field
The present invention relates to an apparatus for an internal combustion engine and which for each cylinder, with the associated piston, has at least one inlet valve and at least one exhaust valve for controlling the connection between the combustion chamber in the cylinder and an intake system and an exhaust system, respectively. A rotatable camshaft, with a cam, is utilized and which is designed (configured) to interact with a first cam follower and a second cam follower in order to switch between two different operating modes.
2. Background
There are numerous examples of the need to be able to adjust the valve lift in inlet and/or exhaust valves of an internal combustion engine. Such examples include the activation/deactivation of a compression brake system on an internal combustion engine for heavy road vehicles; that is, providing additional valve movement that is only operative during engine braking. Another example includes the generation of valve lift curves of differing width of the Miller-cycle type, for example, for use at different operating points in the engine working range. Another example is for utilization in the complete deactivation of valve movement when isolating certain cylinders at partial load and the like. Still a further example includes utilization to institute internal exhaust gas recirculation via the exhaust valve or via the inlet valve.
When the facility is required for fixing a rocker arm part in relation to another part, for example, an actuator is required that can overcome the forces occurring between the various parts without any impact occurring when the movement of the rocker arm parts in relation to one another approaches the limit positions. The movement of the rocker arm is controlled by a cam that defines the movements and accelerations that constituent parts must perform in order to achieve the required lifting movement, thus giving rise to forces and torque in the mechanism. These accelerations must be multiplied by the masses and mass moment of inertia, and any spring forces acting on the mechanism must be added in order to obtain the total forces in the system.
It is desirable that apparatuses for producing additional openings of valves should not extend significantly in a longitudinal direction in the space available for the engine valve mechanism. For example, the high compression ratios that occur in modern diesel engines mean that the valve mechanism must be designed for very high contact pressures. Furthermore, this type of engine may be fitted with some form of compression brake system, which requires space for actuating members. Consequently no apparatuses for switching between two valve operating modes should encroach on the existing compression brake system. It is also desirable to be able to perform this switch from one mode to another in a simple way.